This invention relates to apparatus and a method for transferring material from the surface of a body of water to subaqueous depths, and in particular to deep sea bed locations.
The disposal of waste material is a major problem and is one which is increasing at an alarming rate. In many instances, waste materials are disposed of in the sea. Some materials are simply dumped from ships or pumped into the water. Such surface dumping leads to widespread pollution of the surface waters due to dispersal of waste matter as it sinks towards the sea bed. This can have a deleterious affect on the marine environment over a wide area.
In order to avoid or substantially reduce the risk of wide spread pollution during the disposal of large quantities of waste material in the sea, it is desirable to deposit the waste on or close to the sea bed either at deep water sites (for example 4000-5000 m depth) which have little or no marine life and negligible local currents, or in shallow water sites where a regime known as "subaqueous capping" is operated to localise the deleterious effects of dumping waste in such waters. Under this regime, waste with a high contaminant content ("dirty waste") is first dumped from a ship at a chosen shallow water site, and then waste with a relatively low contaminant content ("clean waste") is dumped over the top. This tends to cover the dirty waste with clean waste, thereby "capping" the dump site.
Particularly when waste material is to be deposited at deep water sites, the transfer of the waste material to its intended disposal location presents a number of difficulties. For economic operation, it is desirable to transfer the maximum quantity of material to the disposal site in the minimum space of time. For deep water sites, continuous disposal through, for example, a pipeline connected to a waste storage facility on board a vessel is not practicable.
An object of the present invention is to provide apparatus and a method for transporting material from the surface of a body of water to a subaqueous level (typically the sea bed) in an efficient manner.
The process of waste disposal preferably takes place from a ship which may be held stationary over a selected subaqueous site by means of a dynamic positioning system comprising thrusters and satellite navigational aids. The ship advantageously has sensors (such as sonar transponders) mounted beneath the hull which allow monitoring of the sea bed and monitoring of any objects beneath the ship.